For more than a decade, it has been conventional to operate control apparatus during delayed shutoff after the ignition of an engine has been switched off in order to provide for specific conditions which are advantageous for a renewed start of the engine and the further operation thereof. These conditions include especially a monitoring as to whether conditions are present with respect to the engine which require a hot start. It is conventional to burn off the hot wire in the delayed-shutoff phase on internal combustion engines having a hot-wire air-flow sensor. For this purpose, a method is available developed over a decade ago according to which the wire is not burned off with the same intensity in each delayed-shutoff phase to increase its operational life; instead, an intense burn-off operation always takes place only after several weaker burn-off operations. Furthermore, it is possible in the delayed-shutoff phase to statistically evaluate data from the previous operating cycle in order to obtain, for example, adaptation values for improved further operation.
All known delayed-shutoff methods operate in such a manner that for ending all delayed-shutoff functions, the time span elapsed since switch-off of the ignition is measured and delayed-shutoff functions are terminated after pregiven time spans have elapsed. At the beginning of the delayed-shutoff phase, all functions are started such as the following: time measuring functions for the hot start, the burn-off of a hot-wire air-flow sensor, the displacement of the throttle flap in the event that the latter is electrically controlled from a completely closed condition into such a position in which the throttle flap cannot become jammed and the statistical evaluation of data and the like.
It has been shown that there are always cases, although fortunately few in number, wherein experiments have shown that, when the engine was operated without a delayed-shutoff phase, it is easier to start the engine again than if the delayed-shutoff functions had been performed.